Regulation of arc lamps



1942' A. BUCHWALD 2,291,947

REGULATION OF ARC LAMPS Filed March 21, 1940 IN V EN TOR.

Patented Aug. 4, 1942 REGULATION OF ARC LAMPS Arno Buchwald,Berlin-Haselhorst, Germany, as-

signor t0 Kislyn Corp-oration, New York, N. Y., a corporation ofDelaware Application March 21, 1940, Serial No. 325,271 In GermanyFebruary 17, 1939 2 Claims.

This invention relates to the regulation of arc lamps.

It is known to compensate for the consumption of arc lamp electrodeswith the aid of an adjusting device which advances the electrodes inaccordance with the arc lamp current and/ or the arc lamp voltage. Tothis end, relays have been employed which control a particular auxiliarydevice, for instance, which switch in and out a motor.

When regulating arc lamps in such a manner by means of a relay it hasproved particularly disadvantageous in that the magnitude determiningthe position of relay changes immediately after initiating the controlmotion, whereupon the relay is immediately operated again. The advantageof this regulation consists therefore in the fact that the consumptionof the electrodes is compensated for when being advanced at very shortintervals, whereas the regulating device or the relay is very oftenoperated. In this manner an extremely rapid wear and tear is caused. Itis true that also connections are known in which the feed of theelectrodes is influenced by a relay consisting of a magnet and armature.If the armature is attracted upon the energization of the magnet, aconsiderable reduction of the magnetism is necessary in order to bringit back again into its original position. From the original position thearmature returns to its operating position upon a further considerableincrease of the magnetic flux. Such control devices are, however, fartoo insensitive and cannot be sufficiently adjusted. To remove the abovedrawbacks are lamps are regulated according to the invention with theaid of a relay in such a manner that a control motion caused by therelay is suppressed if owing to the changed values of current and/orvoltage the relay releases another control motion as a result of thechanged position of the relay. It is particularly advantageous to employa circuit closed by the relay and to maintain the circuit with the aidof an auxiliary device if the relay itself has already again opened thecontact.

Only when operating another relay contact, the automatic holding deviceof the first circuit is brought out of operation so that this circuit isreplaced thus eliminating the regulating effect caused by the same.

A relay which may be satisfactorily used in connection with thisinvention is illustrated and described in detail in my copendingapplication Serial No. 325,270 filed March 21, 1940.

Further details of the invention will be apparent from the descriptionof an embodiment of the regulating arrangement according to theinvention in connection with the accompanying drawing.

An arc lamp has its electrodes energized from any suitable currentsource as shown and is provided with two electric motors for feeding theelectrodes with the aid of suitable intermediate means. The negativeelectrode is influenced by the motor I, whereas the positive electrodeis regulated by the motor 2. The speed of the driving motors may becontrolled by potentiometers 3 and t respectively, energized by a powersource (not shown) through terminals 5 and 6. This source of power forthe driving motors may be the same source as that for operating the arc,but obviously can be an entirely independent source of the same ordiiierent voltage. The circuit extends from the terminal 5 through thechange-over switch 1 on the one hand through the potentiometer 3 to theterminal 6 and on the other hand through the potentiometer 4 to theterminal 6. Between this terminal and the movable contacts of thepotentiometer the driving motors l and 2 are connected through thechange-over switches 8, 9 and [0, in Which case the speed of the motorsmay be varied by adjusting the potentiometer contacts allotted thereto.The switches l, 8, 9 and H] are connected by a common actuating memberin such a manner that either the just-described circuit is renderedpossible which causes the motors for feeding the electrodes to operatecontinuously or that the switches operate an automatic control device bythe position shown in the drawing.

The connection so far described need not take into consideration theerrors as regards the proper distance between the electrodes caused by anon-uniform consumption of the electrodes and by fluctuations of theoperating voltage. For this purpose, a control system is providedcooperating with a relay, which system may cooperate with the regulatingarrangement so far described and arranged in the arc lamp together withContact pairs Hi to Hi. In this automatic regulating arrangement isprovided a contact system B designed, for instance, in the form of amoving coil relay and whose reed I2 is influenced by the magnetic fieldof the coil l3 which receives its current through the contact pair H3,H4 from the shunt 14 arranged in the main circuit of the arc lamp to beregulated. The magnetic field produced by the coil i3 is thereforeproportional to the arc lamp current so that the position of the reed I2of the relay R is controlled in accordance with the arc lamp current.

The reed I2 of the relay R plays between contacts I5, I6, I1 and I8, ofwhich the contacts I6 and I1 come directly into engagement with the reedI2, whereas the contacts I and I6 are only closed by the contacts I6 andI! designed as trailing contacts. Upon a movement of the currenttraversed reed I2, for instance, in a direction towards the contact I6,the latter is first closed; i. e., the connection between I2 and I6 isestablished and upon a further deflection of the reed I2 also thecontact I5 comes into engagement so that the connection between I2, I6and I5 is established. In the same manner the contact I! and also thecontact I8 are closed upon the movement of the reed I2 in the otherdirection.

The reed I2 is connected through the fuse I9 and the contact pair Hz tothe change-over switch I, which in the position shown-switching in theautomatic regulating deviceestablishes a direct connection with theterminal 5 connected to the power source. The contacts I5, I6, I1 and I8are, however, connected through the coils of auxiliary relays 20, 2| and22 and through the protective resistor 23 by means of the contact pairII 9 to the terminal 6 connected to the power source.

The coil I3 of the relay R is so connected to the shunt I4 lying in thecircuit of the arc lamp that upon a decreasing current the reed I2 ofthe relay R moves in a direction towards the contact I6 and closes thelatter if the arc lamp current attains a given difierential below thedesired value. chosen as 1% of the desired value by correspondinglyadjusting the spring carrying the contact I6. The contact I 6 closesthen the circuit through coil of the auxiliary relay 2| to which theswitches 2 I and 2 I are allotted. The switch 2| is parallel connectedto the contact between the reed I2 and the contact I6 so that thecircuit is maintained not only through this contact but also through theswitch 2| of the auxiliary relay 2|. The switch 2|" also operated by theauxiliary relay 2| closes the circuit extending from the terminal 5through the change-over switch I, the contact pair Hz, the fuse I9, theswitch 2|", the change-over switch 24, the contact pair H5 and theswitch 8 to the driving motor I of the negative electrode and thenthrough the change-over switch 9, the contact pair 6, the change-overswitch 25, the regulable resistor 26 and the contact-pair ||9 to theterminal 6. The motor I will therefore move the negative electrodetowards the positive electrode with the speed regulable by the resistor26, thus increasing again the current flowing through the arc lamp. Uponthis increase of current, the relay coil I3 is impressed through theshunt I4 with an increased voltage so that the reed I2 of the relay Rcomes out of engagement with the contact I6. Upon this interruption theflow of current through the auxiliary relay 2| is, however, notinterrupted, since the switch 2| operated by the coil of the relay 2|continues to maintain the circuit. The value of the resistor 26 ischosen in such a manner that the speed of the motor I correspondssubstantially to the normal consumption of the electrodes or is somewhathigher. In this case the reed of the relay I2 may be moved withincertain limits by the variable arc lamp current without varying theadjusted rate of feed of the relative electrodes so that a smoothoperation or This differential may be burning of the arc lamp is ensuredwithout the need of permanently efiecting a subsequent regulation.

If the arc lamp current becomes greater than the desired value, forinstance, by the fact that the negative electrode has been advanced toorapidly, the contact I! is closed. The current flowing through the relayR flows now no longer through the switch 2| and the coil of theauxiliary relay 2| which always offers a certain resistance, but throughthe reed I2 and the contact I! to the protective resistor 23, thepurpose of this resistor being to prevent an unduly high current fromflowing through the reed I2 of the relay R. Because of this shortcircuit current ceases to flow through the coil of the auxiliary relay2| and the switches 2| and 2| open. While the switch 2| disconnects onlythe coil of the relay 2| from the power source, the switch 2 Iinterrupts the current flowing through the motor I so that the drivecomes to rest and the negative electrode is no longer advanced. Thelatter consumes gradually and increases the are so that the arc lampcurrent returns again to its desired value. In this manner the relayreed I2 coming out of engagement with the contact |'I interrupts theshort circuit of the relay 2|, without releasing any further controloperation. Only after the arc lamp current has been further reduced thereed I2 comes into engagement with the contact I6, closes therefore thecircuit for the auxiliary relay 2| and puts the motor I again intooperation through the switch 2|. The play of the contacts is repeated inthe manner described above so that the arc lamp current is kept withinthe range determined by the distance of the contacts I6 and H from thereed I2. By changing the distance of the contacts from the reed I2 it isthus possible to adjust any accurate regulations and number ofregulations.

It may happen that the arc lamp current attains a value below the valueallotted to the contact I6, for instance, is reduced by 10%. This willalways be the case if the arc lamp is not yet in operation but thevoltage is applied to the terminals 5 and 6 and the electrodes are stillapart. When the current falls considerably below a given value the reedI2 of the relay R will close the contact I5 through the trailing contactI6 and also energize the coil of the auxiliary relay 20 besides the coilof the auxiliary relay 2| already energized by the contact I6. Thisrelay 20 operates not only the switch 26 which supplies energy to therelay 20 independently of the position of the relay reed I2 but also theswitch 20" which short circuits the resistor 26. The motor I of thenegative electrode is therefore supplied with a particularly strongcurrent through the switch 2| also closed by the auxiliary relay 2| andthrough the change-over switches 24 and 25; i. e., it moves the negativeelectrode at a considerably higher speed towards the positive electrodethan is the case if only the auxiliary relay 2| is energized and theresistor 26 is effective in the circuit. The auxiliary relay 20 actuatestherefore a device which brings about a rapid movement, thus ignitingwith the lamp in operation the arc lamp or increasing the arc lampcurrent within a very short period.

The switch 2|)" will, however, not be open again if the relay reed I2releases the contact I5 through the contact I6, since the coil of relay20 is continuously energized through the switch 20'. Also when thecontact I6 comes out of engage ment with the contact reed I2 the motor Irunning at a high speed will not yet be disconnected, since the switch2| supplies current also to the coil of relay 2| independently of theposition of the reed I2. Only when the desired value of the arc lampcurrent is exceeded even by a slight amount and the contact I1 is closedthe auxiliary relay armatures firmly held by the coils of relays 2|] and2I drop, since these coils are short circuited through the contact I'I.Upon the armatures being released the switches 20', 20", 2| and 2I areopened; i. e., the motor I comes to rest. The adjustment of the arc lampcurrent to the desired value is effected therefore very rapidly alsoupon a considerable drop below a given value of the arc lamp currentwithout, causin the contacts of the regulating arrangement to oscillatepermanently.

It may happen that the arc lamp current exceeds the desired value by aconsiderable amount, for instance, if the electrodes come intoengagement upon the ignition of the arc lamp. In this case the reed I2of the relay R will not only close the contact II but also the contactI8, whereby current is supplied to the coil of an auxiliary relay 22,whose armature closes the switch 22' and brings furthermore the switches24 and 25 into the switch position not shown in the drawing. A circuitis then closed extending from the terminal 5 through the switch I,contact pair I I2, fuse I9, switch 25, contact pair Ila, switch 9 to thedriving motor I and then through switch 8, contact pair II5, switch 24and contact pair H9 back to the terminal 6. However, since the motor Iis traversed by current in the opposite direction, the motor runsbackwards at a high speed provided that the field excitation remainsconstant and moves the electrodes apart until the reed I2 of the relay Rleaves the contact I'I. At this moment the current flowing through thecoil of the auxiliary relay 22 and maintained constant by the switch 22independently of the position of the contact I8 is interrupted so thatalso the switches 24 and 25 return to the position of rest shown; i. e.,deenergize the motor I. The negative electrode of the arc lamp is,consequently, moved--when the desired arc lamp current is exceeded by aconsiderable value-back a distance at a great speed, which is to bemaintained under the prevailing operating conditions. Also in this casethe regulation of the electrode is effected independently of theengagement of the contact I8 by the switch 22' so that the regulationinitiated at a great speed is effected up to the desired value of thecurrent.

In the embodiment shown the arc lamp current flowing through the shuntI4 influences through the relay R and motor I only the position of thenegative electrode, whereas the position of the positive electrode isnot influenced. However, in order to keep the positive electrode in theproper position with respect to the mirror, for instance, when using thearc lamp for cinema projectors or searchlights a thermal switch 2! maybe provided which, for instance, is closed if an image of the are or ofthe positive electrode projected by a known device is projected in thecase of a false position of the anode close to the thermal or heatsensitive member. Current then flows from the terminal 5 through theswitch I, the contact pair I I2, the fuse I9, the contact pair II1, theswitch 21, the contact pair He and the coil of the auxiliary relay 28through the contact pair IIg back to the terminal 6, so that thearmature of the auxiliary relay 28 short circuits through the switch 29a regulable resistor 30 which is arranged in the circuit of the feedmotor 2 allotted to the positive electrode. While in normal operationthe motor 2 by suitably adjusting the resistor 30 advances the positiveelectrode in accordance with the normal consumption, the resistor 39 isdisconnected with the aid of the thermal switch 21 during theconsumption of this electrode and therefore an accelerated feed of thesame is brought about. The speeds of the motors are chosen in such amanner that only relatively slow movements are imparted to theelectrode, whereas the motor I imparts a relatively high speed to thenegative electrode when using the rapid or backward movement. When thearc lamp is in operation the positive electrode will therefore maintainpractically its position, whereas the negative electrode is at firstapproached with the aid of the device for a rapid movement and is thenrapidly moved backwards with the aid of the device for the backwardmovement to form an arc.

What is claimed is:

1. In a control system for regulating the adjustment of the electrodesof an arc lamp having electrically operated means for adjusting at leastone of its electrodes, a main relay in circuit with the electrodes, anauxiliary relay operable by said main relay, a circuit controlled by theauxiliary relay connecting the electrode adjusting means to a source ofelectrical energy, a holding circuit established by the operation of theauxiliary relay to maintain the circuit to the electrode adjustingmeans, and means controlled by main relay acting only in response tovariations of predetermined magnitude in the operating characteristicsof the arc lamp to release said holding circuit thereby interrupting thecircuit to the electrode adjusting means.

2. In a control system for regulating the adjustment of the electrodesof an arc lamp having electrically operated means for adjusting at leastone of its electrodes, a main relay in circuit with the electrodes, anauxiliary relay operable by said main relay, a circuit controlled by theauxiliary relay connecting the electrode adjusting means to a source ofelectrical energy, a holding circuit established when the auxiliaryrelay operates to close the electrode adjusting circuit, said holdingcircuit locking the auxiliary relay in position to maintain the circuitto the electrode adjusting means, and mean controlled by main relayacting only in response to variations of a predetermined magnitude inthe operating characteristics of the'arc lamp to short circuit saidholding circuit thereby releasing the auxiliary relay to permit it tointerrupt the circuit to the electrode adjusting means.

ARNO BUCHWALD.

